Joe Friel's Blog is for the serious endurance athlete who wants to stay current on the science and art of training for sport. Here you will find Joe Friel's thoughts and ideas before they are published anywhere else. You may also visit www.TrainingBible.com for more detailed and free content. Joe's training plans are available at www.TrainingPeaks.com.

09/22/2013

Aging: What's Behind the Decline?

There’s
no doubt that there is a loss
of athletic performance with aging. We will never see a
70-year-old athlete take gold in the Olympic Games marathon. Sports scientists
have offered several
reasons why age robs us of the ability to compete with young endurance
athletes at the highest level. In my last post I described a couple of studies
examining the loss of muscle mass as this is one of the commonly accepted
reasons for slowing down as we get older.

What’s
not fully understood is why muscles atrophy. We know that muscle fibers get
smaller and even seem to disappear later in life. It has to do with some
combination of the well-documented physiology of aging and the less understood changes
that typically occur in lifestyle resulting in our being less active as we get
older. How much of the loss of performance can be attributed to these two
variables – physiology and lifestyle – is open to speculation. Which causes the
greater drop in performance over the years? The research I described here on muscle and aging still
leaves the question unanswered.

But
many scientists have come to conclusion that the major contributor to the
decline is not really age, but rather lifestyle, especially a reduction in
strenuous activity. They believe the physiology-lifestyle balance is around
30-70. In other words, 70% of our lowered performance may be explained by
changes in lifestyle (training) with the changes due to aging accounting for
only 30%.

Besides
muscle wasting, there are other physical changes that science tells us to
expect as we get older. Perhaps we can find an answer as to what the balance is
between physiology and lifestyle as the root causes in one of them.

One other such critical marker of aging is aerobic capacity (VO2max). This is one of the most
studied markers of endurance performance. Perhaps we’ll find the answer here.

But
before getting into that, let’s review the big picture of what accounts for our
performance in endurance sports. Science tells us there are three physiological
predictors of your endurance performance regardless of age:

* Aerobic capacity has to do with how much
oxygen you use per minute relative to your body weight when at a sustained, maximal workload. This intensity can be maintained for only a handful of minutes by
highly fit athletes. The greater the aerobic capacity, the greater the
likelihood you can produce a high level of performance.

* Lactate threshold is the percentage of aerobic
capacity at which you begin to “redline” meaning that you start to experience
an increase in the acidity of muscles and body fluids. Highly fit athletes can
maintain this intensity for about an hour.

* Economy measures how efficiently you
use oxygen to produce a given output (pace, speed, power). The greater the
economy, the less wasted oxygen (and energy) and therefore the better your
performance.

Of
these three, science tells us that the best marker of age-related performance
decline is aerobic capacity and secondarily lactate threshold while economy is
a distant third and seems to remain stable (Tanaka, Tanaka, Wiswell). That
economy would not be a good age-related performance predictor makes sense since
after decades of training and racing the movement patterns of older athletes
have become well-honed. So it’s aerobic capacity that we need to examine
closely to see what might be expected as the candles on the birthday cake
increase.

Aerobic
capacity is largely dependent on how much oxygen-carrying blood your
cardiovascular system can deliver to the muscles. So the starting point is your
heart’s stroke volume (how much blood is pumped per beat). Among the many other
aerobic capacity determiners are aerobic enzymes found in the muscles. Both of
these and a bunch of other aerobic capacity determiners – such as how elastic your
blood vessels are and how much red blood cell-building, natural levels of EPO
you produce – have been shown to decline with age.

Ok,
so aerobic capacity decreases as we get older. I can accept that. But by how
much, and more importantly, why? Let’s go back to the research to look for
answers.

There
is quite a bit of research on age and aerobic capacity. How come? I suppose it’s
because aerobic capacity is so easily measured in the lab (it’s been a common
procedure since the 1920s) and it doesn’t require invasive techniques such as taking
muscle biopsies or pricking the skin to draw blood (ouch!).

Since
VO2max testing has been so common for so long we now finally have some
longitudinal studies in which athletes are tested over several years to see how
their aerobic capacities change. This offers hope of finding the affect of
lifestyle on performance as distinct from the aging process. Let’s look at a
few such studies.

Research tells us that the decline has a lot to do with how active we are as we
get older. For example, a paper released in 2000 examined the combined affects
of age and activity level over time (Wilson). The researchers reviewed 242
studies on aging and VO2max involving 13,828 male subjects. Each of the
subjects was assigned to one of three groups based on how active they were:
sedentary, moderately active exercisers and endurance-trained runners. Aerobic
capacity was highest in the runners and lowest in the sedentary. No surprises
there. The aerobic capacity changes per decade of life were sedentary -8.7%, active
-7.3% and runners -6.8%. So if at age 30 a man had a VO2max of 60 and for the
next 30 years didn’t exercise and lived a “normal” life (sedentary) he could expect
his aerobic capacity at age 60 to be around 46. If moderately active it would
be about 48. And if he trained it would be in the neighborhood of 49. Those are
not significant changes.

But
the study further reports that the subjects who were “endurance-trained runners”
significantly decreased their volume (miles/kilometers run per week) and training
intensity as they got older. I’ve found that as a common practice with aging
athletes. There could be many reasons for this (which I’ll address in the
following post). So maybe it’s not simply working out that maintains aerobic
capacity and therefore, in part, race performances, but rather how much
training you do and how intensely you do it. This is an important lesson

That
aerobic capacity declines with aging and reduced training is not surprising.
I’ve mentioned “use it or lose it” several times in this on-going discussion. This
brings us back to the question of what the balance between age and lifestyle is
when it comes to performance.

Three
other reviews of the literature in the last decade or so examined the
relationship between aging and training status to figure out the relative
contributions of both (Hawkins, Wiswell, Young). They confirm that reductions
in training volume and intensity are primary contributors to the loss of
aerobic capacity with advancing age.

Let’s
dig a little deeper to find which is more important to the maintenance of
aerobic capacity with aging from a strictly training perspective – volume or
intensity. The answer may provide some insights into how to train as age sneaks
up on you – assuming you want to maintain, or at least slow, the drop in
performance which probably first becomes apparent in your 50s and greatly
accelerates somewhere beyond 70.

In
the 1970s a team of researchers at the University of Illinois measured the
aerobic capacities of 24 masters track runners who were 40 to 72 years old at
the time (Pollock). Ten years later they were retested. Over the decade all
continued to train but only 11 were still highly competitive. The other 13 quit
racing and decreased their training intensity. The competitive athletes
maintained their training intensities and, consequently, their aerobic
capacities. There was no significant change. The non-competitive, low-intensity
group lost about 12% of their aerobic capacities over 10 years.

So what’s the bottom line here? The research team led by Wilson showed
us that the changes in aerobic capacity with aging are not too different
between sedentary subjects and runners who
reduce their training. Several other studies also showed us that decreases
in training workload have a significant impact on aerobic capacity with the key
being intensity, according to the Pollock paper. When training intensity was
maintained by master runners over a 10-year period, aerobic capacity remained
unchanged. When training volume remained about the same but intensity
decreased, aerobic capacity dropped by an average of 1% per year.

That’s a clear message. It isn’t just exercising slowly for long periods
of time that keeps our performance, at least in terms of aerobic capacity, from
dropping rapidly; it’s primarily the intensity of the exercise that matters.
That raises new issues (problems?) that I’ll address in my next post.

Comments

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Joe - great info. I understand that Aerobic Capacity might decline from, say, 60 to 50 over years. But if I'm only sustaining a VO of 35 on a 12 hour ride or 50 mile run, do I care? I'm guessing my LT might also drop by the same ratio, so I guess my VO=35 would be closer to my LT, causing a higher level of exertion, more glycogen use, etc. Is that the issue for sub-maximal efforts with a lower VO2Max?

Dave B--The longer and therefore slower the event is the less likely VO2max is a predictor of performance. That doesn't mean _unimportant_ tho. But one of the other 2 (LT or economy) must be high then. For ex, Frank Shorter's VO2max was tested at 70. Rather pedestrian for a world class athlete (usually at least high 70s). He made up for that with extremely efficient movement.

Hi Joe: As always, very good research. .as cycling race season winds down, your research makes me (a mid 50's guy) nervous to totally shut down the intensity. . how about one set of 5x5 at 110% of ftp per week just to slow down the aging process?
Thanks
Markj